This research seek to gain general knowledge about factors contributing to the etiology and natural history of Post-Traumatic Stress Disorder (PTSD) through an examination of individuals injured in motor vehicle accidents (MVAs), some of whom subsequently develop PTSD. Two-hundred (200) individuals who are involved in a MVA and subsequently seek medical attention because of the MVA will be carefully assessed approximately 1 month after the MVA. In addition to details concerning the MVA and the subject's reactions to it, patients will be assessed for current psychopathology, especially presence of PTSD or sub-syndromal PTSD, using the ADIS-R, for previous diagnosable psychopathology using the SADS-L, and for current psychological state and psychophysiological reactivity to cues reminiscent of the MVA. One-hundred (100) age, sex, SES matched-controls who have not had a recent MVA will also be assessed. All MVA victims will be followed up using the LIFE methodology of Keller et al (18) for at least one year, and up to 2 years when initially positive for PTSD or sub-syndromal PTSD. Factors related to development of PTSD, its remission (with or without treatment) and its recurrence will be identified as will factors associated with delayed onset of PTSD. In addition, descriptive information on MVA-related PTSD, using state-of-the-art assessment procedures, will become available.